Demon World

The Demon World, also known as Hell, the Underworld, the Netherworld, and the Devil Kingdom, is a location seen in the Devil May Cry series. A grim, treacherous place, it is the hellish realm which parallels the Human World, and serves as the homeland of the many demons which populate the games, including the Legendary Dark Knight himself.

The Demon World is an extension of the original darkness that covered the universe before the coming of light. It is in the Demon World where natural demons are born, and it is within the boundaries of this realm where demons are capable of unleashing their full power and strength, with many demons being severely weakened while away from it.

From the few glimpses of the Demon World seen throughout the series, it can be observed that the realm does not follow the same natural and physical laws as the Human World, with examples such as gravity being inverted, ceilings serving as floors, self-rearranging environments, and even naturally occurring events of entirely localized space-time displacement.

The Demon World is also implied to serve as the afterlife for depraved and evil humans, similar to many Abrahamic religions, as mentioned in some of the library files in the original Devil May Cry; however, no deceased humans have ever been observed trapped in the realm in any of the games.

History
Two thousand years before the events at Mallet Island, the Human World and demon world were locked in a bitter war. Because humans were weaker than demons, the outcome of the war seemed inevitable. Until Sparda, born of the demon world, awoke to justice, and turned against his kind to aid the humans. He alone defeated the armies of Hell, and sealed away the demon world using his own Yamato, his blood, and the blood of a human priestess.

Description
The Demon World is a confusing place, to say the least. It seems to consist of many different planes and realms, with several corresponding to specific biomes, such as the  which Berial rules.

Rule
The Demon World is usual controlled by the most powerful demon or being present at the time. Previously, an unnamed Demon King ruled before years before Mundus was born two millennia ago, in which he ruled for thousands of years even after Sparda's defection and sealing away the Demon World from the Human World.

One hundred years prior to Dante's involvement with the Protectorate, a god called Argosax rose to power and became the new king, having subdued all the demons within the realm barring Sparda. He was then later defeated by the swordman and as a result, the leadership went back to Mundus and kept his position until his demise by Dante.

After his demise, Berial was his successor as the ruler of the Demon World until he was killed by the devil hunter that had killed it's previous rulers.

Moving between Worlds
It is possible to move from the Demon World to the Human World. This is done through different types of portals. It seems that while these portals require some sort of magical method to open or create (magic being exclusive to demons), they can only be opened, or are much easier to open at the least, from the Human World. There are many different portals between the two worlds, of all different sizes, the largest of these portals having been closed by Sparda. It seems that lesser demons are much more able to travel between worlds, but it requires a much larger portal to allow more powerful demons to cross. In Devil May Cry 2, the pathway to the Demon World is much less defined than a simple portal; a gradual transition that involves using multiple Sacrilege's to slowly bring the Demonic and Human realms together. However, this process appears to be completely separate to the traditional portal, as Dante makes a solid transition to the Demon world for the final boss of the game.

Devil May Cry
Typically, the realm is laden with devils, mostly mid/high-ranking ones. Mundus' abode consists of an organic and fleshy interior which pulsates as though it were alive. His throne room however, has an almost heavenly atmosphere. It is very pristine and is made of a lustrous, marble-like material. It is illuminated by bright, immaculate rays of light and is accompanied by pleasant cathedral music.

Devil May Cry 2
The landscape appears to be nothing short of a vast, seemingly everlasting landscape with a charcoal-like black ground amidst a crimson horizon and the dark skies with blurred faces ever watching with malice.

Devil May Cry 3
In this game, Dante visits surrealistic parts of Hell, though there are some major differences between them.

Locations in the Main Hall
The locations include Unsacred Hellgate, Road to Despair and End of the Line. These work as transit locations, and there are no major fights, although Mission 20 (the final battle with Vergil) is entirely set in the Unsacred Hellgate. All of these locations are in some kind of enormous hall. The walls are painted in a manner similar to Temen-ni-Gru’s interiors. Pieces of wall are torn off and the top of the Tower can be seen through the hole. The path is created from stones floating nearby that will regroup as a path once Dante starts walking in it.

Damned Chess Board
Not much to say about this Damned Chess Board as it is a “simple” board. There, you will “play” chess with the Damned Chessmen. However the chessmen can activate or deactivate at will. Dante cannot damage them while they are deactivated. Also, the King can shift positions with the Rook regardless of their places in the chessboard. Finally, all the pieces move simultaneously, not taking turns like in the actual chess.

Lost Souls Nirvana
A white void with stairs, walls, and waterfalls flowing from nowhere. The stairs here are crossed in angles, and what is sometimes a wall can become a floor and vice versa. Dante cannot jump or execute attacking moves in this realm, only running and walking. The role of “lost souls” is played by all of the bosses (except for Vergil, Lady, Jester, and Arkham) which need to be defeated in order to proceed

Nirvana of Illusions
A small mirrored room with some Abysses and a green mirror which is moving between niches in walls. An inscription can be seen in the room, stating, ”Substance projects Image and Image punishes Substance”. This means that the Abysses are projections from the green mirror and only by breaking the mirror will the Abysses be defeated.

Infinity Nirvana
A location with a semi-circle pathway and a giant hourglass in the middle. Abysses are also present in the room, and they need to be defeated before the sand in the clock runs out. This place seems to be floating somewhere in the Hall, as its painted walls can be seen, though they whirl around quickly.

Forbidden Nirvana
The location where Dante fights Arkham. Around the small arena, some rocks rise, and the room itself is filled with some purple liquid. In the center, there is a hole where the Force Edge and the Perfect Amulet falls through it after the battle.

Room of Fallen Ones
An endless lake of blood, with massive statues of demons, supposedly Fallen Ones, sunken in it. Dante can somehow walk on the liquid’s surface, though Abysses, which are made from blood, can move freely in it. This is, presumably, the location where the unseen battle between Vergil and Mundus takes place.

Leviathan
It is stated in the Character file: “Leviathan’s body is a gateway to the hell of jealousy” so its Core is part of The Demon World as well.

Role in Devil May Cry
Dante travels to the Demon World in every game except for Devil May Cry 4, in which it is only mentioned.

Devil May Cry
In the game's last three missions, Dante enters the Demon World to confront Mundus.

Devil May Cry 2
Dante enters the Demon World once more to confront the dark realm's former master Argosax the Chaos.

Devil May Cry 3
In this game, Dante visits surrealistic parts of Hell, though there are some major differences between them. Dante travels into the Demon world to stop Arkham & his nefarious plans to steal the Force Edge and harness it's power to rule the Earth with Demon infesting it.

Devil May Cry 4
Though Dante doesn't visit the Demon World, it is mentioned several times. Most notably the Hell Gates were created so Demons could enter the Human Realm.

Trivia

 * It is possible to travel back to the summit of Temen-ni-Gru from the Unsacred Hellgate.
 * The music playing in the Unsacred Hellgate is very similar to the one in Mundus' throne room in Devil May Cry.
 * The design of the Lost Souls Nirvana is based on M.C. Escher's Relativity.
 * In the credits scene of Devil May Cry 3, the base of Temen Ni Gru can still be seen. This suggests the tower remained present in the city, albeit in a dormant state, after the portal to the Demon World was closed.